In June, the Rapid Excavation and Tunneling Conference (RETC) will be the next powerhouse of information-sharing on underground construction hosted in North America, across three busy days.
RETC is sponsored by the Society for Mining, Metallurgy & Exploration (SME) and this time the major bi-annual gathering is located in Boston, MA. The main conference and exhibition runs over 12-14 June and will be held at the Sheraton Boston Hotel, located downtown, and directly connected to the Prudential Center and the Hynes Convention Center.
The Underground Construction Association (UCA), a division of SME, is sponsoring dozens of students to attend RETC 2023 in support of their career aspirations.
Immediately before the main event, on 11 June, an excellent training opportunity is available for aspirants as well as the more seasoned for an update or refresher – ‘Shotcrete in Underground Construction’, taught by a range of industry experts.
When the main conference commences, the packed Technical Program is as follows, arranged in 4 tracks:
Monday 12 June
Morning – 4 tracks are:
design build projects; difficult ground; geotechnical consideration; and, hard rock TBMs and tunnels
Afternoon – 4 tracks are:
design; ground control approaches and methods; microtunneling and trenchless tunneling; and, shafts, caverns, and mining; plus, there is a session of an owners forum panel
Tuesday 13 June
Morning – 4 tracks are:
ground support and final lining; international projects; tunnel rehabilitation; and, new and innovative technologies-1
Afternoon – 4 tracks are:
future projects; new and innovative technologies-2; pressurized face tunneling; SEM applications and projects
Wednesday 14 June
Morning – 4 tracks are:
contract practices; health & safety and sustainability; risk management; and, project planning Here, we highlight the Day I tracks and planned papers to whet the appetite for the full Technical Program that runs until the middle of Day 3.
MONDAY, 12 JUNE
Morning
Design Build Projects (Track sponsor: HNTB)
? Focus on Scarborough Subway Extension, in Toronto, with a focus on use of steel fibre reinforced concrete for a large span single bore tunnel. Paper by Strabag and Arup
? A review of standard and design approaches for waterproofing systems for underground structures, including interpreting limits between them in pursuit of permanent seal. Paper by Renesco
? From Manila, in The Philippines, comes a focus on use of EPBM tunneling in an urban setting for a water supply tunnel on NBAQ4 project, which also involved mined excavation. Paper by Arup and Manila Water Co
? Looking a progressive design build (PDB) via a case study for a gravity-flow water pipeline tunnel in California. Paper by Barnard Bessac JV, Arup, and Tanner Pacific A review of the completion of the LA Metro Regional Connector Transit project, which included bored tunnels, an SEM cavern and three underground stations, plus cut and cover tunnels. Paper by VN Tunnel and Underground, and LA County Metropolitan Transportation Authority
Difficult Ground (Track sponsor: Stantec)
? On the 50th anniversary of its opening, a spotlight on the challenges of investigation for and construction of the high-elevation Eisenhower Memorial Tunnel, in Colorado. Paper by Stantec, and Colorado Department of Transportation
? A look at the geological challenges for construction of the JWPCP Effluent Outfall Tunnel project, in Los Angeles. Paper by Pini Group, and Dragados
? Taking a focus on the part of the Purple Line Extension of LA metro, the paper looks at preparing for and executing the bored pressurized face tunneling through a confined gas zone. Paper by Traylor Bros, Golder Associates, and LA County Metropolitan Transportation Authority
? Second Narrows Water Supply Tunnel project, which involved conventional deep shaft excavation in variable weak rock, in Canada. Paper by McMillen Jacobs (now Delve Underground), Greater Vancouver Water District, WSP Golder, Traylor Aecon
Geotechnical Consideration
? A review of how the lump-sum, design build procurement was undertaken with particular reference to development of the geotechnical baseline report (GBR). Paper by CB3A, Aecom, Stantec, and Narragansett Bay Commission
? Two presentations on the use of artificial ground freezing (AGF): for its adaptable use on smaller tunnels and varied geometries, such as cross passage and adit construction; and, ways to horizontally excavate into soil that is a frozen temporary support to an excavation. Both papers by SoilFreeze
? Discussion of the ground improvement challenge with extensive jet grouting in glacial soils to permit both EPBM boring and micro-tunneling for the Lower Olentangy Tunnel project, in Ohio. Paper by Black & Veatch, City of Columbus, DLZ, McMillen Jacobs (now Delve), Schnabel Geostructural D&C, and Granite Construction
Hard rock TBMs and tunnels
(Track sponsor: Walsh Construction)
? From Norway comes two projects in papers by Skanska Norge – one looking at construction of the Nedre Fiskumfoss upgrade and replacement hydropower plant with major tunnel and cavern excavations in the far north, in a paper by Skanska Norge; and, another discussing multiple rock cavern construction for a new water supply project in Oslo.
? And, with a focus on the Italian-Austrian Alps, the experience of using risk prediction tools in TBM tunneling on the Mules 2-3 Lot of the Brenner Base Tunnel is discussed. Paper by Systra.
? From Canada, the focus is on construction of the multiple and varied tunnel and shaft structures for the Coxwell Bypass Tunnel project, in Toronto. Paper by Jay Dee Contractors and Jaydee Canada ? Also in Toronto, the achievements in TBM tunneling below Lake Ontario for the Ashbridges Bay Outfall Tunnel will be discussed. Paper by Robbins
? Wastewater is again the focus in a paper looking this time at the Sister Grove Outfall Pipeline project, in Texas, which used TBMs to excavate rock and mixedface conditions similar to others previously bored through. McMillen Jacobs (now Delve)
? Considerations for enhanced probe drilling and pregrouting design on hard rock TBMs are discussed, with reference to Lower Meramec and Jefferson Barracks tunnels. Paper by Robbins
Afternoon
Design (Track sponsor: HNTB)
? A look at drill & blast tunneling and deep shaft construction, all for water intakes on a quarryto- storage reservoir conversion project that was executed using collaborative design development. Paper by Schnabel, Guy F. Atkinson Construction, Arcadis, Loudoun Water, and Black & Veatch
? Design focus on the new large underground structures for a parallel Central City Tunnel below Minneapolis to increase the stormwater drainage system’s capacity to handle heavy rainfall events. Paper by Hatch, CNA Consulting Engineers, and City of Minneapolis
? From New York comes a review of design for a deep section of cut and cover tunnel capable of supporting high-rise buildings, as part of the Gateway program that could enable airspace rights real estate development. Paper by WSP and Amtrak
? Review and discussion of corrosion analyses of liners in gravity sewer tunnels, including fibre reinforcement and carbon footprints. Paper by Parsons
? Underground construction in support of high-energy physics R&D is discussed in the case study of a tunnel for the particle accelerator in LCLS-II-HE project, in Menlo Park, California. Paper by Mott MacDonald and SLAC National Accelerator Laboratory
Ground control approaches and methods
? Evaluating the loading effects of constructing a high-rise building and consequent estimated tunnel behaviors in the two underground metro lines below, in LA, and then comparison with construction monitoring. Paper by McMillen Jacobs (now Delve), Geotechnologies, Jamison Properties, and LA Metro
? Examination of ground movements during construction of a gravity-flow water pipeline tunnel constructed by EPBM, in California, and developed using PDB (discussed in a paper earlier in the day). This paper by Arup and JCK Underground
? Description and construction update of varied small bore tunneling and shaft works for the Bay Park Conveyance project, in Long Island, NY, that will divert treated effluent. Paper by WSP.
Microtunneling and trenchless tunneling (see box)
Shafts, caverns, and mining
(Track sponsor: Walsh Construction)
? Construction description of the Shoreline Storage Tunnel project, part of Project Clean Lake, in Cleveland, using a large diameter EPB machine plus shafts and pipe-jacking. Paper by McNally Tunneling
? Review of using artificial ground freezing (AGF) for deep shaft excavation for the upper geology before advancing below into gneiss bedrock on Tunnel No3 of New York City’s water supply system. Paper by Keller, McMillen JA Engineering, and Walsh Construction
? Looking at shafts again, this time with two methods of works – the design and construction of excavation support with secant piles in glacial soil, and controlled blasting in complex sedimentary strata with site-specific controls in an urban setting. Paper by Mueser Rutledge Consulting Engineers, Civil & Building North America, Barletta, and Stantec
? Another look at underground construction for high-energy physics R&D, this time considering the development and performance of large span caverns at depth in South Dakota. Paper by Arup and Fermi Research Alliance
TRACK: MICROTUNNELING AND TRENCHLESS TUNNELING
Monday, 12 June – afternoon session
Track sponsor: Stantec
Chairs: Jay Shankar, Amtrak; Leah McGovern, STV
There are to be four papers presented in the first day’s afternoon session track on Microtunneling and Trenchless Tunneling – the only dedicated track during RETC 2023, although small bore, microtunneling and pipe-jacking are among trenchless methods that feature in parts of some other projects to be described in papers to the conference.
The first paper is entitled ‘The Versatility of Tunneling and Trenchless Methods for Sustainable Grid Construction’, and is by Peter Schmaeh and Dr Marc Peters of Herrenknecht.
Description of the details to be covered discuss how underground high voltage power cables are coming to be important in replacing above-ground and vulnerable overhead lines when seeking to support development of a sustainable power grid that features renewable energies. The details say that public concerns and environmental awareness have been enabling new, modern power cables to be installed underground with smart tunneling and trenchless solutions in both urban and countryside locations, and for crossings and landfall sections that bring ashore cables tied to offshore generation facilities, such as windfarms. Methods from the tunneling and pipeline industries enable flexible solutions and alignments to be developed, including versatile tunnel concepts and installation of protective pipes, such as enabled by Herrenknecht’s E-Power Pipe and Direct Pipe systems.
The second paper is ‘Curved Microtunneling to Reduce Disruption in City Environment’, by Daniel Cressman of Black & Veatch.
The paper describes the work on a sewer in Toronto to install a concrete pressure pipe by microtunneling methods to take the alignment under a wide road and then stay within a narrow permitted corridor for the project. Slurry microtunneling was used to deal with mixed face conditions under the high groundwater level in the urban environment and the curved alignment was used also to help negotiate subsurface obstacles, including other existing utilities, condominium tiebacks and a bridge structure.
Third of the four papers is ‘Missouri River Intake Screen Structure and Tunnel: Overcoming Underground Challenges to Build Vital Infrastructure’, by Ryan Ward of Michels Trenchless.
With microtunneling selected as the excavation method with the highest probability of success in river valley deposits (sands, gravels, cobbles and boulders) under high hydrostatic head, the construction work on the bank of the Missouri River, in North Dakota, sunk a shaft with secant piles for the drive to get underway. The tunnel linked to a cofferdam in the river, where intake screens would be installed for the operational phase of the project which is part of the Red River Valley Water Supply Project. While the tunnel is relatively short and small bore, the works required extensive planning and preparation, and focused execution, to overcome the geological challenges.
The fourth and final paper in this afternoon track focuses on small scale tunneling – ‘Northeast Boundary Tunnel Project: First Street Connector Tunnel and Mount Olivet Road Diversion Sewer Design and Construction’, by Brierley Associates and The Lane Corporation.
The Northeast Boundary Tunnel (NBT) project in Washington, DC, involves construction of a long CSO drainage tunnel with multiple connections, including seven shafts, in an urban setting. Discussed are to be two of the connection points into the large tunnel – First Street Connector and Mount Olivet Road Diversion Sewer, respectively. The NBT project is being developed by DC Water.
